1. Field of the Invention
This invention generally relates to devices used and methods employed in connection with surgical procedures affecting the heart and, more specifically, relates to an epicardial immobilization device and method of use, the principal purpose of both being to reduce the movement of, or to immobilize, a region of the cardiac epicardium during surgery to permit the heart to be operated on while it is beating.
2. Description of the Related Art
Surgical treatment and repair of vital organs, especially of the heart, requires a high degree of precision on the part of the physician and surgical team, and such precision heretofore has been difficult to achieve when the organ is functioning, because movement of the organ can compromise the accuracy and relative safety with which an operation successfully can be accomplished. Accordingly, and with respect to cardiac cases in particular, it has been conventional to temporarily stop the heart from functioning to effectively immobilize it while an operation is being performed. Most commonly, this is accomplished by diverting blood flow to the heart through the use of an external pump, such as with a device referred to as a "heart-lung machine," which is intended to substitute for the function of the organ so that blood can be sufficiently oxygenated and circulated through the body during surgery. The heart thus effectively will be immobilized, and the physician and the surgical team can render treatment on particular parts of the heart, or the vessels supplying or leading to or from it, with greater precision than would be possible if the heart were beating.
Clearly, though, it easily is appreciated that diverting the function of a vital organ to an artificial mechanical substitute can entail significant trauma under any circumstances and, depending on the overall condition of a particular patient, the prospect of such trauma can be such as to contraindicate life-sustaining or quality-of-life-enhancing treatment. Thus, there has been an effort to develop surgical techniques which obviate the need to resort to a heart-lung replacement pump, so as to allow an operation for treatment or repair of the heart or of its associated vessels while the heart is functioning and beating. The class of patients for which such techniques have been deemed appropriate, however, has been limited by the precision implicated by a particular procedure, because of the challenges inherently presented by a beating heart. Continuous movement of the heart renders any surgical operation performed on it or its associated vessels more complicated and more difficult than would be experienced if the organ were non-functional and, hence, effectively immobilized. Accordingly, use of techniques which involve surgical treatment of a beating heart has been limited.
One device that has been employed to immobilize the beating heart during surgery comprises a supporting ring in the shape of an open "O" and having an attached rigid arm. The supporting ring includes a base provided with a plurality of vacuum cups that are connected to a pneumatic circuit. The vacuum cups, when supplied with a suctioning force, are used to temporarily secure the device to the epicardium. Experience with this device has been less than optimum, insofar as post-surgical lesions and hematomas have been detected that are associated with the areas of the epicardium to which the vacuum cups were attached. It also is of some significance that this device is relatively expensive to use.
When an object of the surgery is treatment of the vessels of the heart muscle (e.g., the coronary arteries), another complication often is encountered due to the presence in the vasculature of occlusions, such as atheromatous plates or other restrictions, that result from atherosclerosis or another disease or condition known to cause vascular obstruction. Because these vessels carry blood (except when totally occluded), blood flow through the vessels must be curtailed while the surgery is being performed, such as operations to suture venous or arterial bridges, in order to prevent obscuring the surgeon's view of the operational field.
In the past, blood flow through the vessels of interest temporarily has been prevented through the use of ligatures, sutures or clamps which, when tightened, close off the vessel. When occluded vessels, such as coronary arteries exhibiting atheromatous plates, are involved, great care must be taken in choosing the site along the vessel at which to place a ligature, suture or clamp. This is the case because, if the compression associated with the tightening of such a ligature, suture or clamp is applied to an area in the vessel that is affected by an occlusion, the tightening force can cause the occlusion to fracture. Such fracture then might result in the partial dislodgement of the occlusion when the compressing device is removed, the dislodged portions can cause further obstructions to blood flow, such as clot formation, or other problems as the portions move through the vasculature of the patient.
In an attempt to reduce the risk that the ligatures, sutures or clamps used to temporarily prevent blood flow will cause the fracture of atheromatous plates, before placing the compressing devices, surgeons have relied on palpating the vessels before the ligatures, sutures or clamps are positioned, in order to make sure that the intended site of placement is flexible rather than rigid, which would be the expected condition of the vessel if it were characterized by an occlusion. Palpation is effective for detecting plates when the plates are present in the epicardial, or outer, surface of the lumen of a vessel, but is a less effective technique when the plates are disposed in the vessel laterally. Palpation is not an especially useful method of locating plates when the same are present in the endocardial, or inner, surface of the vessel lumen.
The devices to temporarily prevent blood flow in the vasculature of interest, however, commonly have been applied to regions of the vessels that are more distal to the heart than is optimum, owing to the fact that presence of atheromatous plates is more difficult to discern in those regions.
What has been needed, then, and what heretofore has been unavailable is an apparatus and method which permit a beating heart to be held effectively immobile while a surgical operation is being performed while concurrently allowing the operating field to be kept free of obscuring blood with a reduced risk of dislodging vascular occlusions as a result of the temporary prevention of blood flow through the vessels supplying the heart. The present invention satisfies these needs.